Aluminum borate catalyst compositions

ABSTRACT

Certain crystalline aluminum borate catalyst supports containing about 8-25 weight-percent of B2O3 are found to provide unusually stable and active catalysts for high-temperature chemical conversions, particularly exhaust gas conversion, when prepared by precalcining shaped composites of alumina and boria at temperatures between about 1,250* and 2,600*F., prior to the addition thereto of active metal or metals. Calcination at below 1,250*F. is found to yield amorphous catalysts of inferior activity, while at temperatures above 2,600*F. drastic reductions in surface area may occur.

United States Patent 1191 1111 3,856,702 McArthur Dec. 24, 1974 [54] ALUMINUM BORATE CATALYST 3,133,029 5/1964 Hoekstra 423/2132 x COMPOSITIONS 3,331,787 7/1967 Keith et a1. 252/439 [75] Inventor: Dennis P. McArthur, Yorba Linda, FOREIGN PATENTS OR APPLICATIONS Calif. 1,184,331 12/1964 Germany 252/432 1,299,123 6 1962 F 252 4 2 73 Assignee: Union 011 Company or California, 3

Los Angeles Cahf Primary ExaminerPatrick P. Garvin [22] Filed; Nov, 16, 1972 Attorney, Agent, or FirmLannas S. Henderson;

' R h d C. H rt ;D S f d pp No: 306,984 10 ar a man can and or Related US. Application Data ABSTRACT [63] c i i q n f Sen NO, 269,544, My 7 Certain crystalline aluminum borate catalyst supports l972,abandoned. containing about 825 weight-percent of B 0 are found to provide unusually stable and active catalysts [52] us. Cl 252/432, 252/477, 423/213.2, for high-temperature chemical con rs ns, pa 423/2135, 423/279 larly exhaust gas conversion, when prepared by pre- [51] Int. Cl B01j 11/82 calcining shaped composites of alumina and boria at [58] Field of Search 252/432, 477; 423/213, temp ratur s twe a t 1, 50 and ,60 423/213.4, 213.5, 279 prior to the addition thereto of active metal or metals. Calcination at below 1,250F. is found to yield amor- [56] References Cited phous catalysts of inferior activity, while at tempera- UNITED STATES PATENTS tures above 2,600F. drastic reductions in surface area 2,118,143 5/1938 Benner et al. 423 279 x may Occur 4 2,125,743 8/1938 Sweeney .7 252/432 X 20 Claims, N0 Drawings .doned. BACKGROUND AND'SUMMARY OF INVENTION ALUMINUM BORATE CATALYST COMPOSITIONS RELATED APPLICATlONS This applicationisa continuation-in-part of applica tion Ser. No. 269,544, filed July 7, 1972, now abancal and thermal stresses encountered in catalytic converters for the conversion of nitrogen oxides, carbon monoxide, and unburned hydrocarbons in automobile exhaust gases. Some materials e.g., alpha alumina, are suitably inert and stable, but general do not give a final catalyst havingthe volumetric. activity that can be obtained from the same quantity of active metal or metals supported on other less stable supports such as gamma alumina. An optimum combination of activity and stability has been difficultto achieve.

Alumina-boria catalyst composites are known in the art, and in particular were extensively investigated at one time in the catalytic cracking'art. However it was in general considereddesirabl'e to retaina substantial surface area, above about l50 -m /g inthe finalcatalyst composite, and for this reason it was the practice to calcine such catalysts at relatively low temperatures, below about 1,200F., which are below the temperature-required for the formation-of crystalline aluminum borates. At the other extreme, US. Pat. No. 3,l72,866 disclosescatalyst supports prepared by calcining alumina-boria mixtures containing less than 5 weight-percent boria at temperature of l-,600-l ,800C (2,l92 3,272F.), under which conditions the boria is apparently sublimed out of the composite, and a final alpha alumina support having a surface area below 0.5 mlg is produced.

It has now been found that for purposes of producing a catalyst of maximum. activity and stability for high temperature, vapor phase conversions such as exhaust gas conversions, a much superior support is produced by calcining certain alumina-boriacomposites within the temperature rangeof about I,250 2,600F. Calcination within this range appears to produce a definite crystalline phaseof 9Al O .2B O and also in most cases a crystalline phase of ZAI O B O Although calcining such composites at temperatures below or above the specified range can produce supports of adequate stability for some purposes, it appears that within the range of about 1,250 2,600F., an optimum combination of crystallinity, porosity, surface area, and/or chemical properties is produced, such that a distinct maximum activity is achieved from active metals supported on such supports. Also, such catalysts exhibit excellent thermal and mechanical stability up to temperatures of about 2,500 3000F., dependingmainly upon the type of active metals present. They are also 2 highly resistant to shrinkage at temperatures'up to at least about 2,500F.

DETAILED DESCRllPTlON I Suitable alumina starting materials for the supports of this invention may comprise any one or more of the so-called transition aluminas, including species now commonly identified as chi, delta, eta, gamma, kappa, and theta aluminas. The various hydrated aluminas such as boehmite, gibbsite and bayerite'may also be utiaspowdered B 0 or as a thermally decomposable precursor thereof such as orthoboric acid, tetraboric acid, metaboric acid, ammonium pentaborate, ammonium tetraborate. various organic compounds of boron such as the boric acidesters, alkyl boranes and the like. The preferred B 0 source is ordinary orthoboric acid, H The proportion of boron compound employed should be adjusted to provide a finished catalyst support wherein the weight ratio of B O /Al O is between about 8/92 and,25/75, preferably between about 10/90 and 20/80. If the final composition contains more than ZSweight-percent B 0 a liquid phase will be formed at calcinationor conversion I temperatures above 470C. (878F.), with resultant fluxing and loss of surface area and porosity (Nature, vol. 195, July 7, I962, pages 69-70). Aliquid phase is also formed at temperatures above l.,035C( l,895F.) if more than 14 weight percentof B 0 is present,.butin the B 0 concentration range of 14-25 percent, this liquid phase is not necessarily detrimental. A minimum of about 8 weightpercent B 0 appears-to be required to achieve adequate thermal stability. j

It should be understoodthat, unless otherwise specified, when boron contents or ratios are expressed herein as B 0 total boron content is intended, including boron present as aluminum borates and as free B203.

Conventionalcompounding procedures may be employed in compositing the two materials. It is necessary to provide an intimate admixture of the finely divided materials such as may be achieved by grinding, mulling, or ball milling the dry powders "together, following which the mixture. is shaped into a porous, selfsupporting aggregate, as by tableting, prilling, extruding, casting or other well known techniques to form cylindrical pellets or extrudates, spheres or other granular forms ranging in size fromabout'l/32-inchup to about 12-inch. For prilling, extruding, or casting, the powdered mixture is ordinarily wetted with sufficient water or other liquid to form a suitable plastic or flowable mixture, while tableting is ordinarily performed by compressing the slightly moist but sensiblydry powdered mixture into suitable tableting'dies.

Instead of initially dry mixing the alumina and the boron compound, the powdered alumina can be homogenized into an aqueous or other solvent solution of boric acid to provide the. proper consistency for prilling, spray drying, extruding, casting, coating or the like. Also, alumina powder can be impregnated with aqueous or other solvent solutions of boric acid and then calcined to form an alumina boria powder which can then beformed into any desired shape prior to the high temperature calcination to transform the alumina-boria to aluminum borate. A hydrous alumina gel, prepared by any of the many methods known in the art, can be peptized by the addition of boric acid in the desired amount, and the peptized gel can then be spray-dried by conventional methods to form an initimate aluminaboria mixture which can be subsequently transformed into a shaped aluminum borate. These methods, and other equivalent methods which give extremely intimate admixture, are preferred in that they permit the final calcination to be carried out at temperatures and- /or times in the lower ranges described hereinafter. A particularly suitable class of solvents for these modifications comprises liquid aliphatic polyhydroxy compounds such as glycerol, glycols, and the like, in which boric acid is more soluble than in water.

In one form of casting or molding, a monolithic block may be prepared by incorporating suitable combustible fibrous material into the fluid slip, which is later removed by combustion to give a monolithic body traversed by suitable l/32 Ar-inch diameter channels for fluid flow from one face of the monolith to the opposite face. Other conventional methods for fabricating monolithic structures may also be utilized.

, Another form of monolithic support can be prepared by depositing a thin layer of the alumina-boric acid slurry (in water or other solvent) over the surfaces of a preformed monolith composed of inert, low-surfacearea materials such as alpha alumina or cordierite, which in themselves possess insufficient surface area and/or porosity for catalyticpurposes. Several such monolithic supports are commercially available, notably those composed of cordierite or spodumene in the form of corrugated septa consolidated together in layers or rolls to provide a multiplicity of parallel channels from about l/32-inch to A-inch in diameter traversing the structure. To render these monoliths suitable for use herein it is desirable to coat the channel surfaces (external and internal) thereof with a layer of the alumina-boria composite ranging in thickness from about 0.0005 to 0.01 cm. This may be conveniently achieved by immersing the monolith in a water or glycerol solution of boric acid or other soluble boron compound in which the alumina component is dispersed to give a viscous slurry.

All ofthe above support forms comprise, after drying at temperatures of, e.g., 200 600F., a shaped, porous, cohesive aggregate of finely divided alumina and boria or boria precursor. The shaping into a porous, cohesive aggregate (whether granular, monolithic, or membranous) preferably takes place prior to the critical calcination step. For purposes of this invention the :oxide support materials may also be admixed with the ,alumina-boria composite'prior to the final shaping operation. Examples of such materials include silica, magnesia, zirconia, titania, and the like.

After drying, the shaped support is then subjected to the critical calcination step, as by heating in air or other gases for about l-48, preferably l] 2 hours at temperatures between about l,250 and 2,600F., preferably about l,450 2,300F. The operation may be carried out in-conventional manner as, e.g., in a rotary kiln, fired oven, or by passing hot gases through a fixed bed of the support. It is preferable to raise the support material to the final calcining temperature over a period of about I to 5 hours. The overall severity of the calcination should be controlled to produce in the first instance a substantial, X-ray-detectable phase of crystalline 9Al O;,.2B O corresponding substantially to the following diffraction pattern:

Table l dA 1/1, dA 1/1 dA 1/1,

This phase is normally produced in the form of well defined crystallites having an average size of about 250A., which are easily detectable by X-ray diffraction analysis. Preferred forms of the support will also comprise a relatively minor phase, believed to be 2Al- 0 .8 0 in the form of smaller crystallites having an average size of about l-30 A., and which are usually not as readily detectable by X-ray analysis. This phase (which is believed to enhance mechanical and thermal stability) exhibits the following major spacings:

Table 2 dA 1/1, dA 1/1, dA 1/1, dA 1/1 The size of the crystallites produced in the calcination is the primary parameter governing critical func tional aspects of the support, such as mechanical and thermal stability, porosity, pore size distribution, and surface area. Calcination temperatures in the high ranges tend to produce large crystallites with resultant reduction in surface area and increase in average pore size. Conversely, the lower temperature ranges tend to give smaller crystallites, higher surface areas and smaller pores. These parameters of pore size and surface area can thus be made to vary considerably, depending upon the intended use of the catalyst. In many catalytic-processes extremely high surface areas and pore volumes are not required, or may even be detrimental. ln any case, it is normally desirable to preserve at least about l,'preferably at least about 5, m /gm of surface area, and at least about 0.] preferably at least about 0.2 ml/g of total porosity.

When the ultimate catalyst is intended for use in the conversion of automobile exhaust gases, the calcining should be controlled so as to give a support having a surface area between about 5 150, preferably about 100 m /gm, with a porosity of about 0.2 0.8, preferably 0.3 0.7 ml/gi One aspect of the invention, which is important in many processes in which the finished catalysts may bc utilized, is to ensure that substantially no free boria is present in the support when the active metal component is added. Free B 0 melts at about 860F. and dev'elops a substantial vapor pressure at temperatures above about 1,200F. Hence, during calcination follow ing the addition of active metal salts, and/or during subsequent use of the catalyst at high temperatures, any free boria becomes very mobile and active as liquid and/or vapor, andtends to combine with and deactivate most of the common transitional metal catalyst components. Also, if any water is present, volatile metaboric acid may be formed, which becomes very corrosive to ferrous metals at elevated temperatures, as is molten B 0 itself. In contrast to the hydrothermal instability of B 0 the compounds 9Al O .2B O and 2Al O .B O appear to be hydrothermally stable up to temperatures of at least about 3,540F. and l,895F., respectively.

The maximum boria content weight-percent) specified herein corresponds substantially to the compound 2Al O;,.B O (the 2:lcompound). The concentration of 13.3 weight-percent B 0 corresponds to the compound 9Al O .2B O (the 9:2 compound). The intermediate concentrations correspond to mix tures of the 2:l and 9:2 compounds. Boria contents below 13:3 percent correspond to mixtures of the 9:2 compound and free A1 0 lt would hence appear that in theory no free boria should be present in the final calcined supports. However, depending upon the intimacy of admixture of the initial alumina and boria components, the temperature and time of calcination and perhaps other factors, some'free boria is usually present in the calcined composites. Also, at calcination temperatures above about l,035C (1,895F). the 2:1

compound breaks down to form freeboriaand the 9:2

compound:

4.5[2Al O .B O 9A| O .2B O 2.588 0 In all such cases where free boria is present in the calcined support, it is usuallydesirable to remove it, preferably' prior to the addition of active metals. A number Table 3 Boron removal. Boron of total Sample Treatment Content, Wt% initially present 1 None 6.91 2 Steaming at l00F for 6.75 2.3

16 hours 3 Calcination at'2200F 5.99 13.3

for 1 hour 4 Leaching with boiling 6.47 6.4

water for 2 hours 1 5 Boiling water leaching 5.92 14.3

for 2 hours NHiOH leaching for 1 hour Leaching with boiling water and/or with warm, con- .centrated NH OH solutions appear to be the most effective treatments. The effectiveness of calcination at 2,200F. (Sample 3) is not readily apparent, for at that temperature some of the 2:1 compound was undoubtedly converted to the 9:2 compound and free boria. Upon gradual cooling however, this free boria would in theory combine with a portion of the 9:2 compound to reform the 2:1 compound.

To illustrate the utilitarian effect of removing free boria, two comparisions were made on exhaust gas conversion (oxidation), using in one experiment a catalyst (A) containing 24 weight-percent B 0 in the support and from which free boria had not been removed, and in the other a catalyst (B) containing the same active metals, but supported on a base which had been leached in boiling water to reduce the B 0 content to [8 weightpercent. The results were as follows:

Table 4 Temperatures required'for- 5071 Conversion,F.

Catalyst Hydrocarbons Carbon Monoxide Run l Run 2 Run l Run 2 A 837 804 934 El 1 to provide a support containing substantially no free A1 0 in order to prevent the formation during subsequent use of relatively inactive aluminates or spinels of the active metal or metals supported thereon. By the techniques described above it is entirely feasible to prepare supports containingless than about 1 weightpercent of free B and less than about 5 weightpercent of free Al O However, in utilizing this excessboria technique, not more than about 40 weightpercent, preferably less than about 30 weight-percent of boria should be employed in the initial alumina-boria mixture. If too large an excess of boria is utilized, such that more than about l0-20 weight-percent of free B 0 remains in the calcined aggregates, such aggregates will tend to disintegrate into a powder or slurry upon subsequent removal of the excess free boria (see US. Pat. No. 3,080,242). An important attribute of the calcined supports prepared as herein prescribed is their mechanical strength, which normally exceeds that corresponding to a crushing strength of 20 pounds for A; inch X /8 inch extrudate pellets.

Following calcination and removal of free boria, the support may be impregnated in conventional manner with a solution or solutions of the desired catalytic metal salt or salts. Any one or more of the transitional metals or compounds thereof may be utilized, the more widely used of such being the metals of Groups lB, llB, VB, VlB. VllB, and Vlll of the Periodic Table, and their oxides and sulfides. Exemplary metals are zinc, cadmium, copper, silver, chromium, molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum. In exhaust gas conversion catalysts, the more commonly used metals are copper, chromium, molybdenum, manganese, iron, cobalt, nickel, ruthenium, palladium and platinum, or combinations thereof. The iron group metals, and the metals of Groups 18, IIB, VB, VIB and VIIB are normally employed in proportions ranging between about 3 percent and 30 percent, preferably about 6-20 percent by weight, based on the corresponding oxides; The Group VIII noble metals such as palladium and platinum are normally employed in smaller proportions of about 0.05 2 percent by weight.

The salts employed for impregnation are preferably those which are thermally decomposable to give the corresponding metal oxides and/or sulfides. Preferred salts are the nitrates, acetates, chlorides, oxalates, sulfates and the like. Following impregnation, the finished catalysts are produced by draining, drying and if desired, calcining at temperatures of, e.g., 500 to l,000F. In the final catalyst the active metal or metals may appear in the free form, as oxides or sulfides, or

any other active form.

A preferred class of exhaust gas conversion catalysts comprises aboutS-IO percent by weight of copper as CuO and about 5-15 weight-percent of iron, cobalt and/or nickel, as Fe O C0 0 or NiO. These metals, especially copper and iron, are apt to bring about severe shrinkage of conventional transition alumina supports at exhaust gas conversion temperatures. But when employed on the supports of this invention, the shrinkage is substantially nil. 1

Another preferred class of exhaust gas conversion catalysts comprises about 0.05 l.0 weight-percent of one or more Group VIII noble metals, particularly platinum and/or palladium, together if desired with 1% to 10% of one or more of the metals, V, Cr, Mn, Co, Ni, Cu, and Zn.

USE OF CATALYSTS Catalysts based on the supports of this invention may be employed to catalyze any chemical conversion in which supported active metals or 'metal compounds may advantageously be utilized. However, due to the remarkable thermal and hydrothermal stability of the supports, catalysts based thereon are most advantageously utilized in chemical conversions carried out at elevated temperatures of e.g., 600 3,000F., and even more advantageously in processes requiring temperatures in the range of about 900 3,000F.

Several general rules can be followed in selecting an optimum support for the particular reaction concerned. Firstly, for reactions carried out at above about l,900F., it is preferred to utilize a support containing less than about l5 weight-percent, preferably less than l3 weight-percent of B 0 so as to eliminate or minimize the formation of liquid B 0 resulting from the conversion of the aluminum borate to the 9:2 compound. For reactions carried out at below about 1,900F., it is preferred to utilize supports containing about 13-25 weight-percent of B 0 so as to obtain maximum mechanical stability and surface area. It is also a general though not infallible rule that reactions carried out at very high temperatures with all reactants in the vapor phase require less porosity and surface area in the support than do reactions carried out at relatively low temperatures and/or with one or more of the reactants in the liquid phase. Where liquid phase reactants are involved, it is hence preferred to utilize supports having a porosity of at least about 0.5 ml/g, and a surface area above about 40 m /g. For vapor phase reactions carried out at temperatures above about I200F., it is normally feasible to utilize supports having surface areas in the low range of about l-20 m /g, and porosities in the range of about 0.2 0.7 ml/g. For low temperature vapor phase reactions, somewhat higher surface areas and pore volumes are generally desirable.

Another factor to be considered in selecting a suitable support is the amount and type of active metal or metals to be added thereto, and the degree of its dispersion on the support. Obviously, where high metal loadings are desired, a primary consideration is high porosity. Generally, higher porosity is obtained at the higher calcining temperatures. In cases where the active metal or metals are added to the support in such manner as to obtain a very high degree of dispersion thereon a relatively low surface area support may suffice, whereas higher surface areas may be required if the activecomponent is not highly dispersed. With the aid of a minimum of judicious experimentation, these general guidelines can be used to effectively arrive at optimum aluminum borate supports for the particular chemical reaction concerned.

Depending to some extent upon the particular reaction involved, any conventional catalytic contacting technique may be employed, including fixed bed, moving bed, fluidized bed and slurry contacting procedures. Normally a fixed bed operation is preferred with the reactants being passed in vapor phase, liquid phase, or mixed phase through a bed of macropellets of catalyst.

While it is obviously impossible to cite all possible chemical reactions in which the catalysts of this invenproduce hydrogen or low BTU fuel gas, dehydrocy-,

clization of C.,' paraffins to produce corresponding aromatic hydrocarbons, dehydrogenation. of .paraffms to form olefins, or of .cycloparaffins to form aromatic hydrocarbons, naphtha reforming to produce high octane gasoline, hydrodealkylation of alkyl aromatic compounds to effect scission of paraffinic side chains from aromatic rings, hydrogenation of olefins and/or aromatic hydrocarbons, hydrodesulfurization and/orhydrodenitrogenation of mineral oilsor fractions thereof,

downstream catalytic converters can exceed 2,000F., I

particularly when the exhaust is rich in unburned hydrocarbons which, with the aid of added air, are being oxidized in the converter. At these temperatures most catalysts lose substantially all of their activity, usually as a result of the formation of inactive combinations between the active catalyst component and the support. However, catalysts based on the supports of this invention are found to maintain their activity for converting nitrogen oxides, hydrocarbons and carbon monoxide at temperatures in excess of 2,000F. A particularly suitable exhaust gas conversion catalyst comprises about 5-l weight-percent of copper as CuO and about -l5 weight-percent of nickel as'NiO.

The hydrogenation of carbon oxides (methanation) to produce methane is generally carried out at temperatures ranging between about 600F. and l,500F. and pressures between about 100 and 1,500 psig. The reaction isextremely exothermic, and much difficulty has been encountered incontrolling temperature rise in the reactor. One widely used-technique involves the recycle of large volumes of product gaseslmainly methane) merely to serve as a heat sink, thus adding greatly to operating costs. Catalysts previously available for this process have been found to become substantially deactivated if temperatures in excess of about l,100 l,200 are reached during methanation, to the extent that theywill not initiate the reaction at temperatures below about l,200F. Some activity at temperatures above l,200F., is usually retained, but at these high temperatures the equilibrium for methanation is unfavorable; it is therefore a practical necessity to carry out a substantial portion of the methanation at temperatures below 1200F. However, it is also desirable to have a catalyst which does not place a ceiling on the permissible exothermic temperature rise; by removing this ceiling the need for expensive temperature control measures is reduced or eliminated. n I

It will hence be apparent that in methanation a catalyst active over the entire temperaturerange of about 500 l ,500F., and 'especially'at temperatures above l,200F., is highly desirable. Also, sincesteamis pro duced during methanation, a hydrothermally stable catalyst is also required. The catalysts of this invention appear to be ideally suited to these requirements. Metals active as methanation catalysts include primarily the Group VIII metals, and particularly nickel, or nickel promoted withcerium. Preferred methantion catalysts for use herein comprise about 5-40 .weightpercent of nickel as NiO supported on the aluminum borate bases of this invention.

'Steam reforming of methane, or C -C paraffins, to

produce hydrogen is the endothermic reverse of the methanation reaction, and is normally carried out at temperatures ranging between about l,500 and 2,000F. The high temperatures and presence of steam again present a problem in activity maintenance, since the same type of catalysts used for methanation are ordinarily used for steam reforming. Here again the catalysts of this invention find particular utility by vi rtue of their hydrothermal stability and activity maintenance. Dehydrocyclization reactions are normally carried out at temperatures of about 850 l,l50F. and pressures of about 0-50 psig. Primary feedstocks comprise paraffin hydrocarbons, preferably normal paraffins, having at least six carbon atoms, e.g., n-hexane, nheptane, n-octane and the like, the corresponding products comprising mainly benzene, toluene, xylene and the like. Active catalytic components for dehydrocyclization comprise between about 0.1 20 weightpercent of one or more hydrogenating metals, preferably the metals of Group VlB andl/or VIII, e.g., nickel, palladium, platinum, molybdenum, etc, and the oxides and sulfides thereof.

Dehydrogenation reactions are carried out under the same general conditions described above for dehydro cyclization, and the same type of active catalytic components are utilized. Substantially any paraffinic or alkyl aromatic hydrocarbon may be dehydrogenated to corresponding unsaturated compounds. For example ethane may be converted to ethylene, propane to propylene, butane to butene or butadiene, cyclohexane to benzene. methyl cyclohexane to toluene, ethylbenzene to styrene, etc. j I

Naphtha reforming operations are preferably carried out at temperatures of about 800-l ,000F., hydrogen pressures ranging between about I00 and 600 psig, and liquid hourly space velocities of about 0.5 5. Preferred feedstocks comprise straight run and/or cracked naphthas boiling in the'range of about 200 450F., while the preferred active catalytic components comprise Group VIII noblemetals, particularly platinum, employed in amounts of about 0.1 2 weight-percent. In catalytic hydrodealkylation, the objective is to effect scission of paraffmic side chains from aromatic rings without substantially hydrogenating the ring structure. To accomplish this objective, relatively high temperatures in the range of about 800 -l,200 are employed at moderate hydrogen pressures of about 300 1000 psig. Operative catalytic components comprise about 0.1 20 weight'percent of one or more hydrogenating metals, preferably metals of Group VIB and/or Group VIII, e.g., nickel, palladium, platinum, molybdenum and the like, or their oxides or sulfides.

In catalytic hydrofining, the primary objective is to effect a selective hydrodecomposition of organic sulfur and/or nitrogen compounds in the feed, without substantially cracking hydrocarbon molecules. For this purpose, temperaturesv in the range of about 500800F., and pressures in the range of about 400 2,000 psig are normally utilized. Operative catalytic components comprise the metalsof Group VlB and/or Group VIII, preferably in sulfided form. Preferred components comprise combinations of nickel and/or cobalt with molybdenum and/or tungsten. Principal feedstocks include gasoline fractions, kerosenes, jet fuel fractions, diesel fractions, light and heavy gas .oils, crude oil residua and the like.

The following examples are citedto illustrate the invention, but are not to be construed as limiting in scope:

EXAMPLES l6 Boehmite alumina powder was ball milled and dry mulled with sufficient powdered boric acid to provide a 20% B 80% M 0 composite, and the homogeneous powder was then mixed with sufficient dilute nitric acid to provide an extrudable plastic mass. The mixture was then extruded into /8-inch diameter pellets and dried. Separate portions thereof were then calcined at various temperatures as indicated in Table l for 24 hours. The samples calcined at l,200 and l,400F. were amorphous, while those calcined at the higher temperatures were highly crystalline. Each of the calcined samples were then impregnated with an aqueous solution of copper nitrate and cobalt nitrate to provide about 4% copper as CuO and 12% cobalt as C0 0 in the final catalyst. After draining and drying at 110C., the catalysts were tested for nitric oxide conversion activity and selectivity, using as the feed a synthetic exhaust gas having the following composition:

Mole

CO 1.0 H 0.33 Q S 010 NO 008 11,0 10.0 Air (0 1.43 (0.3) C0 130 N 74.06

The test procedure consisted in passing the feed gas through the catalyst bed at a gaseous hourly space ve locity of 23,000, measuring NO conversion at about l,000F. (which generally gives 100% conversion), then at successively lower temperatures so as to bracket the 50 conversion temperature and obtain temperature coefficients. From this the 50% conversion temperatures were calculated, based on the first-order rate equation. Selectivity of conversion to nitrogen was determined at l,250 F. (Selectivity is the percent of No converted which was converted to N rather than to NH The latter is undesirable because in most catalytic exhaust gas converters, any ammonia formed is ultimately oxidized back to NO and emitted to the atmo- 45 sphere as a pollutant.) The results of the test runs were as follows:

Table 5 Conversion of NO Support Precalcination Temp, F. for 50% Selectivity Catalyst Temp.,F. Conversion to N 1 L200 920 53 2 1,400 933 66 3 1.600 760 86 55 4 L800 740 86 5 2,000 8l7 63 6 2,200 765 82 It is readily apparent that catalysts 3-6, based on supports which were calcined at temperatures within the preferred range of the invention, were substantially more active and in most cases more selective than catalysts l and 2 based on supports calcined at temperatures below the preferred range. It should not be coneluded however that the temperature range of 1,250" l,400F. is inherently inoperable; as will be shown hereinafter this temperature range is effective when preferred support preparation techniques are utilized.

EXAMPLES 740 Four additional catalysts were prepared as described in Examples l-6, with the, exception that the Al O B 0 weight-ratio was 86/14 instead of /20. Upon testing as described in Examples l-6, the following results were obtained:

Table 6 Conversion of NO Support Precalcination Temp.,F. for 50% Selectivity Catalyst Temp.,F. Conversion to N (amorphous) 8 L400 860 48 (amorphous) 9 1,600 675 94 (crystalline) 10 1,800 672 94 (crystalline) Here again, the superiority of the crystalline supports of this invention is readily apparent.

EXAMPLES lll 6' Six additional catalysts were prepared as described in Examples l*6,except that the catalyst loading was 8% copper as CuO' and 8% cobalt as C0 0 and in two.

cases gibbsite alumina was used instead of boehmite. Upon testing as described in Examples l-6, the following results were obtained:

(crystalline) Gibbsite alumina thus appears to be somewhat more effective than boehmite alumina in the catalyst supports of this invention.

EXAMPLE 17 This example, and the following Example 18, illustrate more specifically certain preferred methods for preparing the support of this invention, as well as the effect of calcination' temperature on surface area and crystallinity.

About ml of dilute nitric acid solution (pH 2.5), 50 g of Mallinckrodt analytical reagent grade boric acid powder, and 80 g of Kaiser boehmite alumina powder were mixed together in a blender to form a milk. Stirring was continued for an additional 15 minutes, whereupon the temperature of the mixture increased to -l75F., and its consistency was that of a fluffy paste. An additional 52 g of boehmite were added to the paste and the mixture was hand stirred with a spatula to form a homogeneous thick heavy paste. The paste was injected into rubber casting mats (forming molds), and the filled mats were then placed in a drying oven and dried in air at a temperature of l l0C for 3 13 hours. Following the drying step, the pellets were removed from the casting mats with an ejection punch. The cast pellets, comprising 20 weight-percent B were hard, strong, and exhibited good form. Individual samples of the pelletswere then given various air calcination treatments with the following results:

In support A, approximately 30 percent of the pore volume is in pores of greater than 100 A diameter,

whereas in support B almost 100 percent of the pore volume is in pores of diameter greater than 100 A.

EXAMPLE 18 About 250 g of ground Mallinckr'odt analytical reagent grade boric acid powder and 660 g of Kaiser boehmite alumina powder were mixed-together and dry mulled for 30 minutes. Mulling was then continued with a steady slow addition of dilute nitric acid solution (pH 2.0). The time of wet mulling was 45 minutes, and 564 ml of nitric acid solution was used. The finished mull was placed in a barrel-plunger type extruder -and extruded through a lsinch diameter die at a pressure of 800 psig. The extrudates were air-dried at room temperature for 16 hours, and then broken up into the desired lengths A inch to Va inch). Individual samples of the extrudates were then given various air calcination treatments, with the following results:

A suitable monolithic catalyst support was prepared as follows:

To 250 ml ofglycerol was added over a 15 minute period 100 g of Kaiser boehmite alumina while stirring and heating to 145C., at which temperature the slurry was aged for 1 hour. An additional 28 g of boehmite was added, followed by aging an additional 20 minutes. Then 33.8 g of granular boric acid was added, whereupon the slurry became thinner and the temperature dropped to 125C. After aging for 35 minutes, an additional 15 g of boric acid was added, followed by aging an additional 65 minutes. The slurry then appeared to be too viscous, so an additional 100 ml of glycerol was slowly added, followed by heating an additional 60 minutes. t

Next, four American Lava 'uncoated cordierite monolithic supports, Al Si Mag 795, of the rolled corrugated type 12/8 were immersed in the slurry and soaked for 15 minutes at 135C, after which they were removed and placed in Gooch. crucibles where the excess coating was removed by vacuum stripping. In addition tosuction below, an air jet was directed from above to clear the flow passages of the monolith of excess coating material. After stripping, the coated monoliths were air dried in an oven at C for 30 minutes, then heated in a furnace to 1,800FL over a 4- hour period and calcined at that temperature for 24 hours.

The surface area of the resulting monoliths were determined by nitrogen adsorption (BET) to be 30 m' /g. This monolith, when impregnated with about 8 weightpercen'tNiC and 3' weigia pemmouofaraviaes a highly active and selective N01 conversion catalyst, which is stable up to temperatures of atleast about 2,200F.

EXAMPLE 20 This example demonstrates that crystalline supports can be prepared at calcination temperatures below 1,400F., if a preferred compounding procedure is employed:

About 650 g of boric acid powder were dissolved in 1,700 ml of hot distilled water, and the solution temperature was raised to 97C. 800 g of alumina powder (boehmite) were added to the boric acid solution with stirring over a period of 30 minutes. The slurried mixture was aged for 15 minutes, during which time its temperature increased from 94 to 130C. The wet slurry was then transferred to a Biichnerfunnel where the excess solution was stripped away, and the filter cake was air-dried for 1 hour. The wet powder was then oven-dried at 220F. for 1 hour and calcined in air as follows: the temperature was increased from 100 to 800F. over a period of 12 hours, and then heldconstant at 800F. for 2 hours, followed by a slow (-16 hours) cooling to ambient temperature.

840 g of the calcined powder were placed in a muller and dry-ground for 30 minutes. 500 ml of concentrated NH OH were added to'the powder and mulling was continued for 10 minutes. Then 470 ml of distilled water were added and the mulling was continued for an additional minutes. The mull was then extruded through a l/8 /s diameter die at 6 00 psig using a piston cylinder type extruder. The extrusions were dried at 1 10C. for] V2 hours in a forced air oven, broken up into small extrudates, and calcined as follows: the temperature was increased from 100 1,200F. over 21 period of 12 hours, held constant at 1,200 F. for 2 hours, and then cooled slowly (-16 hours) to ambient temperature. The properties of the calcined extrudates were as follows:

Table 10 Properties of Alumina-Boria Extrudates Calcincd ln Air at 1200F.

Water Pore Volume Compacted Bulk Density X-Ray Analysis 0.65 cm lg 0.51 g/cm amorphous alumina-boria Table l 1 Crystalline Structure (Crystalline Size in Angstroms) Calcination Time, hrs.

This method of preparation'consideraifiyTeduces the Table l2.-Continued Catalyst Analysis The catalyst of Example 21 was compared for methanation activity in a 6-day life test with a commercial methanation catalyst comprising about 25 weightseverity of calcination treatment required for-crystallipercent nickel supported on an activated A1 0 base zation of the desired aluminum borate structure. This containing about 17 weight-percent ofa calcium alumiis attributed to the excellent dispersion of boric acid nate binder. The test unit consisted ofa 3/4% l.D. tube within a high surface area activated alumina afholding 50 ml of catalyst, giving a 7-inch bed depth, forded by this method of preparation. Any method with a thermocouple well extending longitudinally which results in a high degree of dispersion of the 20 through the catalyst bed so that exothermic temperaboron compound in the alumina compound, i.e., good ture rises (ATs) at each inch of bed depth could be deintimate contact between the reactants, will facilitate tected. With downflow of feed gas in this apparatus, the the solid state reaction between alumina and boria to rate of progressive catalyst deactivation is measured by form aluminum borate, and thus reduce the effective the rapidity with which the peak AT moves downwardly crystallization temperature. Another desirable method through the catalyst bed, signifying deactivation of the is to mix boric acid with a hydrous alumina gel and then catalyst upstream from the peak AT. spray dry the peptized hydrous gel. Using a feed gas comprising 38.5% CH,, 18.6% H 5.0% CO 2 and 37.9% H O by volume, and at a pressure EXAMPLE 2] of 300 psig and a dry gas space velocity of 5,000 v/v/hr, This example illustrates the preparation of a pre theresults were as follows:

Table 13 Results with Catalyst of Example 21 Days on Stream 1 2 3 4 5 lnlet Temp.,F. 918 925 950 925 920 900 Catalyst Bed Temp.F.

A T.Firs1 Inch 11? 163 r 175 180 160 180 A T Second Inch 38 47 50 A T Third Inch 11 0 0 0 0 0 Total A T 155 215 210 230 220 250 Results with Commercial Catalyst Days on Stream l 2 I 3 4 5 6 lnlet Temp.,F. 893 915 905 920 91s Catalyst Bed Temp.F.

A T First Inch 52 40 25 30 20 A T Second lnch 125 115 80 70 A T Third Inch 0 40 55 80 A T Fourth Inch 0 0 O 0 5 Total A T ferred methanation catalyst of this invention.

- The foregoing results show firstly that the Example An aluminum borate l/8 /s extrudate support con- 50 21 catalyst had a higher intrinsic activity than the comtaining about 17 weight-percent B20 3 was prepared essentially as described in Example 20, but was calcined in ai r at 1,800F. for 14 hours and then steamed at 1,000F. for 24 hours. About15 20 g of Ni(NO;;)

6H O w as dissolved insufficient distilled water to give a totalvolume of 1,000 ml. This solution was then used to impregnate 1,000 ml of the support. After draining off excess solution, the impregnated extrudates were then calcined in air at temperatures gradually increasing from l00750F. over a 12 hour period, and held at 750F. for an additional 2 hours. Analysis of the resulting catalyst showed the followin properties: I V

Table 12 Catalyst Analysis Pore volume Compacted bulk density mercial catalyst, for the inlet temperatures in the latter case were insufficient to initiate substantial reaction in the first inch of the catalyst bed, whereas in the former case the first inch of catalyst bed remained highly active throughout the 6-day run. Of even more importance however is the fact that the Example 21 catalyst showed no measurable deactivation, the reaction being driven to equilibrium in the first 2 inches of catalyst bed throughout the run. The commercial catalyst however was deactivating fairly rapidly, as evidenced by the decline in activity of the second inch of the bed and the rising activity appearing in the third and fourth inc. After about 20 days of operation in this manner, the entire bed of the commercial catalyst would be deactivated.

The following claims and their obvious equivalents are intended to define the true scope of the invention:

1 claim:

1. A catalyst composition consisting essentially of a io proportion of a catalytically active component l7 dispersed and supported on a shaped, porous cohesive aggregate consisting essentially of crystalline aluminum borate, said catalytically active component comprising at least one member selected from the group consisting of the metals of Groups IB, IIB, VB, VIB, VIIB and VIII, and catalytically active compounds thereof, said catalyst having been prepared by the steps of:

l. intimately admixing finely divided alumina in a dry or hydrous state with sufficient boria or boria precursor to provide in the finished catalyst -a B O M1 weight ratio between about 8/92 and 25/75;

2. forming the resulting mixture into an aggregate of desired shape for catalytic contracting;

3. calcining the shaped aggregate for a time and at temperatures sufficient to form a cohesive crystalline aluminum borate aggregate having a surface area between about 1 and 150 m lg and a porosity of at least about 0.! ml/g;

4. impregnating the calcined aggregate from step (3) with one or more soluble compounds of said catalytically active component; and

5. calcining the impregnated aggregate to convert said one or more soluble compounds to a catalytically active form.

2. A composition as defined in claim 1 wherein said catalytically active component comprises copper, or an oxide or sulfidethereof.

3. A composition as defined in claim -1 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof. g

4. A composition as defined in claim I wherein said catalytically active component comprises cobalt,,or an oxide or sulfide thereof.

5. A composition as defined in claim 1 wherein said catalytically active component comprises a mixture of copper or an oxide orsulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof.

6. A composition as defined in claim 1 wherein said shapedaggregate is in the form of 1/32 l/2 inch granules. e

7. A composition as defined in claim 6 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.

8. A composition as defined in claim ,6 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof. 7

9. A composition as defined in claim 6 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.

10. A composition as defined in claim 6 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxidesand sulfides thereof.

11. A composition as defined in claim 1 wherein said shaped aggregate is in the form of a monolithic structure traversed by channels of about 1/32 l/4 inch in diameter.

12 A composition as defined in claim 11 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.

13. A composition as defined in claim 11 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof.

14. A composition as defined in claim 11 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.

15. A composition as defined. in claim 11 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof.

16. A composition'as defined in claim 1 wherein said shaped aggregate is in the form of a membranous coating supported on an inert monolithic structure traversed by channels of about l/32 l/4 inch in diameter.

17. A composition as defined in claim 16 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.

18. A composition as defined in claim 16 wherein said catalytically active component comprises nickel. or an oxide or sulfide thereof.

19. A composition as defined in claim 16 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.

20. A composition as defined in claim 16 wherein said catalytically active component comprises a mixture of copper or an oxide o r'sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof. 

1. INTIMATELY ADMIXING FINELY DIVIDED ALUMINA IN A DRY OR HYDROUS STATE WITH SUFFICIENT BORA OR BORIA PRECURSOR TO PROVIDE IN THE FINSHED CATALYST A B2O3/AL2O3 WEIVHT RATIO BETWEEN ABOUT 8/92 AND 25/75;
 1. A CATALYST COMPOSITION CONSISTING ESSENTIALLY OF A MINOR PROPORTION OF A CATALYTICALLY ACTIVE COMPOENT DISPERSED AND SUPPORTED ON A SHAPED, POROUS COHESIVE ENGGREGATE CONSISTING ESSENTIALLY OF CRYSTALLINE ALUMINUM BORATE, SAID CATALYTICALLY ACTIVE COMPONENT COMPRISING AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF THE METALS OF GROUPS IB, IIB, VA, VIB, VIIB AND VIII, AND CATALYTICALLY ACTIVE COMPOUNDS THEREOF, SAID CATALYST HAVING BEEN PREPARED BY THE STEPS OF:
 2. FORMING THE RESULTING MIXTURE INTO AN AGGREGATE FOR A TIME AN SHAPED FOR CATALYTIC CONTRACTING;
 2. A composition as defined in claim 1 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.
 2. forming the resulting mixture into an aggregate of desired shape for catalytic contracting;
 3. calcining the shaped aggregate for a time and at temperatures sufficient to form a cohesive crystalline aluminum borate aggregate having a surface area between about 1 and 150 m2/g and a porosity of at least about 0.1 ml/g;
 3. A composition as defined in claim 1 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof.
 3. CALCINING THE SHAPED AGGREGATE FOR A TIME AND AT TEMPERATURES SUFFICIENT TO FORM A COHESIVE CRYSTALLINE ALUMINUM BORATE AGGREGATE HAVING A SURFACE AREA BETWEEN ABOUT 1 AND 150 M2/G AND A POROSITY OF AT LEAST ABOUT 0.1 M1/G;
 4. impregnating the calcined aggregate from step (3) with one or more soluble compounds of said catalytically active component; and
 4. IMPREGNATING THE CLACINED AGGREGATE FROM STEP (3) WITH ONE OR MORE SOLUBLE COMPOUNDS OF SAID CATALYTICALLY ACTIVE COMPONENTS; AND
 4. A composition as defined in claim 1 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.
 5. A composition as defined in claim 1 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof.
 5. CALCINING THE IMPREGNATED AGGREGATE TO CONVERT SAID ONE OR MORE SOLUBLE COMPOUNDS TO A CATALYTICALLY ACTIVE FORM.
 5. calcining the impregnated aggregate to convert said one or more soluble compounds to a catalytically active form.
 6. A composition as defined in claim 1 wherein said shaped aggregate is in the form of 1/32 - 1/2 inch granules.
 7. A composition as defined in claim 6 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.
 8. A composition as defined in claim 6 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof.
 9. A composition as defined in claim 6 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.
 10. A composition as defined in claim 6 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof.
 11. A composition as defined in claim 1 wherein said shaped aggregate is in the form of a monolithic structure traversed by channels of about 1/32 - 1/4 inch in diameter.
 12. A composition as defined in claim 11 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.
 13. A composition as defined in claim 11 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof.
 14. A composition as defined in claim 11 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.
 15. A composition as defined in claim 11 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof.
 16. A composition as defined in claim 1 wherein said shaped aggregate is in the form of a membranous Coating supported on an inert monolithic structure traversed by channels of about 1/32 -1/4 inch in diameter.
 17. A composition as defined in claim 16 wherein said catalytically active component comprises copper, or an oxide or sulfide thereof.
 18. A composition as defined in claim 16 wherein said catalytically active component comprises nickel, or an oxide or sulfide thereof.
 19. A composition as defined in claim 16 wherein said catalytically active component comprises cobalt, or an oxide or sulfide thereof.
 20. A composition as defined in claim 16 wherein said catalytically active component comprises a mixture of copper or an oxide or sulfide thereof with at least one member selected from the class consisting of iron, cobalt and nickel and the oxides and sulfides thereof. 